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My son is amidextrous and also has this spatial modeling and mathematic ability, not inherited from me. I wonder if this has anything to do with the left and right sides of the brain working more in unison in individuals with these abilities. I also read that Leonardo Da Vinci was ambidextrous and practised mirror writing.

Ian, thanks. I have been racking my brains out to remember who that famous person was that did mirror writing. Leonardo da Vinci was it.

This minireview concerns a new observation on mirror writing. An uncommon form of writing, mirror writing is seen among healthy individuals, but it can also follow a variety of neurological diseases; it is nearly always carried out with the left hand and is more easily undertaken by left-handers. We have found that a particularly high prevalence of left-handed mirror writing has been reported among those whose native languages are traditionally written in a leftward direction, including Chinese, Japanese, and Hebrew. Innate left-handers and those whose languages are written leftward thus share an unusual facility for left-handed mirror writing, an observation that may have implications for understanding hemisphere specialization in relation to handedness.

INTRODUCTION

Mirror writing runs in the opposite direction to normal and with letters reversed, and it is most easily read using a mirror. It is usually written leftward with the left hand, and its occurrence often appears to be linked to the circumstances in which left-handed writing emerges. The characteristics of mirror writing, the circumstances in which it occurs, and many of the theories thought to explain it were reviewed over 70 years,1 and subsequent clinical and theoretical aspects have been briefly reviewed more recently.2

Transient mirror writing sometimes occurs in both left-handed and right-handed healthy children as a normal phase during writing development. In right-handed adults who write with their left hand, mirror writing can be produced at will and for fun, and it is undertaken by lithographers, printers, and others for occupational purposes. Transient left-handed mirror writing is also sometimes observed when conventional writing is no longer possible in otherwise healthy right-handed individuals, for example, after the right arm has been damaged.

Pathological left-handed mirror writing in children has long been noted to be particularly common in dyslexia or more nonspecific "learning difficulties."3 In adults, pathologically acquired mirror writing most commonly occurs in focal diseases affecting the left hemisphere, in particular a stroke that results in a right hemiplegia when writing with the left hand becomes necessary.1, 4 Extremely rarely, left-handed mirror writing after a right hemisphere stroke has been reported. Mirror writing with the left hand has also been associated with diffuse cerebral disorders, including head injury, and various neurodegenerative processes, including Parkinson disease, essential tremor, and spinocerebellar degenerations.2

The reason why mirror writing is usually carried out with the left hand has long been attributed to abductive arm movements being generally considered easier and better coordinated than adductive movements; leftward writing has therefore been held to be the natural direction of writing of the left-hander.1-2 Letters formed leftward would then result in the form of the script being mirrored, and this is the most usual explanation for reversal of letters such as b and d, although other letters such as s and N are also often reversed.

Various theories to account for mirror writing have been proposed, and these have been summarized elsewhere.2 They include:

1. The motor center hypothesis, in which it is postulated that there are motor programs in the brain, with the programs represented bilaterally but in mirror form in the 2 hemispheres. When the left hand carries out writing movements normally carried out by the right hand, it has been suggested that in mirror writing there is a failure to inhibit the natural left-handed tendency to write leftward and in mirror form.
2. The visual hypothesis, in which it is similarly envisaged that there are bilateral visual memory traces (engrams) in the brain, the nondominant (usually right) hemisphere engram being in mirrored form and again normally suppressed. Thus, when suppression is impaired or incomplete, mirror writing with the left hand would result. Conflict between abnormal motor pathways subserving mirror writing and a normal visual monitoring system has also been suggested.
3. The spatial-orientation hypothesis, in which it is suggested that there is confusion in respect of direction and orientation of reading and writing, sometimes associated with spatial confusion. These phenomena may merge with other related phenomena, including difficulties in overcoming the left-to-right directional bias of normal writing, right-left perceptual difficulties, different processing of writing in right and left hemispace, and access to mirrored graphemes when mirror writing is part of more complex mirror and perceptual phenomena.5
4. The involvement of thalamo-cortical circuitry. Rarely, mirror writing may be seen in essential tremor, Parkinson disease, and spinocerebellar disorders. It has been postulated that disruption of thalamo-cortical pathways may be the common underlying factor in these conditions.

Thus, there are both numerous circumstances in which mirror writing occurs and numerous theories invoked to explain the phenomenon, but the unifying feature is that mirror writing is nearly always carried out with the left hand. Furthermore, left-handers often find mirror writing particularly easy.2 We now report a new observation indicating that there is another group of individuals who have a particular facility for left-handed mirror writing.

New Insights

We have observed that a surprisingly large number of reported left-handed mirror writers are those whose native languages have traditionally been written and read leftward. This is evident from various individual reports of Japanese and Chinese patients, most of whom mirror wrote after (usually) left hemispheric vascular lesions, and the polyglot who, following head injury, selectively mirror wrote and read Hebrew script, while normal reading and writing of Polish remained.6

My youngest is left handed writimg, catching baseball, but batted righthanded, shoots gun righthanded, it was interesting, we didn't force any manner of which way he wanted to go, just let him be natural.(Damn him! Of course he'd have to be lefty for baseball, I had to look far and wide in those days and pay more for good lefty gloves)